In known refrigerators, the temperature of spaces or products stored in such spaces is reduced by using a cooling cycle through which an evaporable liquid coolant is circulated. The liquid coolant is introduced in at least one evaporator in which the coolant is evaporated at constant pressure and temperature. Accordingly, the heat content of the spaces or products to be refrigerated is always reduced by mere evaporation of the liquid coolant. This applies even to cases where the temperature of the spaces or goods to be cooled has to be reduced significantly. In such cases, the large temperature difference in the heat exchange performed results in loss of energy and thus, in poor efficiency.
According known measures that have been in use in the technical field concerned, in cases where the temperature of the spaces or goods to be cooled has to be reduced significantly, the energy consumption of the refrigerators applied can be reduced significantly by cooling performed at varying temperatures and/or by pre-cooling the liquid coolant to or at least near to its temperature of evaporation.
Hungarian Patent Specification No. 201141 discloses a method and a device for performing the same, where for reducing the energy consumption of refrigerators the condensed liquid coolant is introduced, for the purpose of its limited expansion, from a liquid collector of the device in a liquid recipient from which the expanding vapour phase of the coolant is being continuously removed by means of a piston-type reciprocating displacement pump. The vapour phase removed is being reintroduced in the path of flow of the circulated coolant at a location between a condenser and a compressor of the refrigerator. This results in that the amount of liquid coolant contained in the liquid recipient is cooled down, by means of limited expansion, to temperature values that are equal or at least near to the temperature of evaporation of the liquid coolant, and the cooled liquid coolant is introduced in the path of flow of the circulated coolant for evaporation. Since upon passing the throttle or feed valve arranged prior to the evaporator a liquid coolant the temperature of which is higher than the temperature of evaporation would always cool down without the reduction of its enthalpy that is associated with great losses of energy, by introducing a cooled liquid coolant in the cooling cycle as disclosed in the Hungarian Patent Specification No. 201141, considerable savings of energy can be realized.
Besides its significant advantages, the known method and apparatus according to Hungarian Patent No. 201141 show a number of shortcomings, too. The liquid coolant looses its pressure while passing the cooling device, and its pressure will be substantially corresponding to its low temperature. Because of this, either the use of a booster pump becomes necessary for its reintroduction in the cooling cycle, or the cooling has to be terminated well before reaching the temperature of evaporation. In addition to this, a liquid collector of enlarged volume has to be foreseen and used in the device because of the necessity of storing, at least temporarily, the liquid coolant content of the liquid recipient during its discharging. Finally, in contrast to conventional ones, larger capacity feed valves are needed for operation because of the reduced temperature difference upon coolant introduction.
The principal object of the invention is to provide an improved cooling method of reduced energy consumption whereby any known cooling apparatus that also includes a device for cooling a circulated liquid coolant, in a quasi-continuous mode of operation by means of its limited expansion, can be operated at improved economics.
Another object of the invention is to provide an improved device for cooling a circulated liquid coolant by means of its limited expansion that would, due to improved process control and changes in design, be free of the shortcomings of the known device referred to further above.
It has been discovered that by combining the possibility of continuously producing a cooled supply of coolant in a refrigeration plant with the fact that the efficiency and thus, the energy consumption of a cooling process depends, with high significance, on the temperature difference of the cooling process, an improved utilization of the liquid heat content of the cooled liquid coolant can be realized for reducing, in an energy saving manner and at least initially, the relatively high temperature of spaces or products to be cooled.